Highly Efficient Light‐Emitting Diodes Based on Self‐Assembled Colloidal Quantum Wells

Nanocrystal-based light-emitting diodes (Nc-LEDs) have immense potential for next-generation high-definition displays and lighting applications. They offer numerous advantages, such as low cost, high luminous efficiency, narrow emission, and long lifetime. However, the external quantum efficiency (EQE) of Nc-LEDs, typically employing isotropic nanocrystals, is limited by the out-coupling factor. Here efficient, bright, and long lifetime red Nc-LEDs based on anisotropic nanocrystals of colloidal quantum wells (CQWs) are demonstrated. Through modification of the substrate's surface properties and control of the interactions among CQWs, a self-assembled layer with an exceptionally high distribution of in-plane transitions dipole moment of 95%, resulting in an out-coupling factor of 37% is successfully spin-coated. The devices exhibit a remarkable peak EQE of 26.9%, accompanied by a maximum brightness of 55 754 cd m-2 and a long operational lifetime (T95 @100 cd m-2 ) over 15 000 h. These achievements represent a significant advancement compared to previous studies on Nc-LEDs incorporating anisotropic nanocrystals. The work is expected to provide a general self-assembly strategy for enhancing the light extraction efficiency of Nc-LEDs based on anisotropic nanocrystals.